The invention relates to a tire protection and/or skid protection for vehicle tires, the tread of which is provided with recesses, which are to receive tire protectors or skid protectors, and with grooves for retaining strands which hold the protectors in their recesses and can move relative to the protectors.
Since, in a tire protector and/or skid protector of this type, the protectors and the retaining strands are arranged in recesses or grooves, the direct contact between the tire and the ground can be improved, compared with the conditions which apply when conventional tire protection chains or skid protection chains, which are supported on the tread, are used.
A skid protection of the above type is known, wherein essentially cruciform skid protectors are mounted in peripheral and transverse grooves located between rows of blocks or ribs and are held by retaining strands which encircle the tire in the direction of running and are located in peripheral grooves (German Patent Specification No. 1,136,597). For a number of reasons, the known construction cannot be fully satisfactory. A first reason is that it is difficult to re-tension retaining strands which run in the peripheral direction of the vehicle tire, on the one hand because of the length of the retaining strands and the large number of the protectors held by each individual retaining strand and, on the other hand, because of the poor accessibility and the difficult conditions for accommodating tensioning elements. A second reason is that the protectors, during the rolling motion of the vehicle tire, tend to execute tilting motions about tilt axes extending parallel to the axis of the wheel, and these tilting motions must be absorbed by the retaining strands in a manner which promotes wear of the retaining strands. Furthermore, it is virtually impossible to combine the protectors, which in the known solution are located in the region of the tread, with a protection for the side walls of the tire. Moreover, it proves to be a disadvantage that, when exchanging individual protectors of the known skid protection, a large number of further protectors must at least be loosened at the same time. Since the retaining strands running in the peripheral direction also pass through the contact area of the tire, an exchange of these strands and of the protectors is, moreover, completely impossible while the vehicle is standing.
An improvement of the conditions of contact between the vehicle tire and the ground is also the aim of a heavy duty tire which is fitted with tire protection. This tire has a tread into which the running network of a tire protection chain has been vulcanised in, in which case it is necessary to take care during the vulcanisation process that the outer surfaces of the vertical members of the tire protection chain in the region of the tread come to lie substantially in one plane with the latter (German Offenlegungsschrift No. 2,109,876). The manufacture of a tire of this type is extremely complicated and expensive. Last but not least because of the different elasticities of the rubber and of the parts of the chain, high shear forces arise under load between the rubber and the parts of the chain, and these forces have the result that the bond between the elastic rubber and the chain members, initially present on vulcanising in, is lost soon after the tire has been put to use.
Moreover, wear occurs on the links between the chain members in the region of the running network, and this cannot be compensated by re-tensioning. The consequence is that parts of the chain emerge from the tire tread and are thus subjected to loads which they cannot withstand. The tread is destroyed and/or parts of the chain drop out of the tread.